I have to convert the audio tracks of my 24 fps movie to match up with retimed 25fps so that it can be exported alongside the 25fps video (just playback speed change) for broadcast transmission.

I need to speed up the audio to match the new shorter duration (96% of the original speed) while keeping the quality of voice, effects and all the other things as high as possible and with the same pitch.

1) My source audio is 5.1 and it needs to be stereo for broadcast. To keep maximum quality, should I do the mixdown or the retime first? Does it matter?

First mixdown to stereo still at 24fps and only after shrink the audio to 25fps duration right ? I'm not asking how to mixdown, I know how to do it, just asking in what order.

2) Do I need a VST plugin to get good results or can Audition achieve good results directly?

A professional I know in the industry had said he had issues getting decent quality results out of Audition and I wasn't sure if a VST plugin might do a better job.

3) If it is possible to do with Audition directly, what are the proper settings for using Audition?

I think I should go for the Effects -> Stretch and Pitch effect (the one in the picture). My duration will be the original * 0.96.**

Adobe Audition CC - Effect -> Stretch and Pitch

What other settings I should check inside that plugin ?

-> Algorithm: iZotope Radious or Audition ?   
-> Lock Stretch Settings to New Duration ?   
-> Vocoder Mode ?   
-> Solo Instrument or Voice ?   
-> Preserve Speech Characteristics ?   
-> Formant Shift ???   
-> Pitch Coherence ???

Could you explain why you pick some settings and not others?

4) Does it matter if I apply the effect selecting all the channels together or do some changes need to be made on individual channels?

I'm concerned about producing panning artifacts, but my guess is to apply the effect to all the channels at same time.

1 Answer 1


(Disclaimer : I cannot test Adobe Audition, the following is based on experience with other products)

1) I would do the downmix first as the time stretch will be applied on less channels, meaning better speed and potentially less artifacts.

2) This you can only tell by trying the Adobe Audition process and checking if it meets your quality criteria. Seeing that the algorithm is based on Izotope, there are chances that the result will be of sufficient quality.

3) What I would try first would be :

  • select the full clip of your downmix (current duration should update), set the new duration to (24 / 25) * current duration

  • check the 'lock stretch settings to new duration'

  • you only want 'stretch', no 'pitch shift'

  • uncheck 'vocoder mode'

  • apply and tests wether playing with other parameters leads to a good result.

4) I would apply the process to the stereo clip and not to individual mono tracks in order to preserve relationship between the two channels.

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